There is no height limit per se for part 15 AM, it's the legth of the ground involved with the height which creates the problem.

Per the letter of the law the transmitter would have to sit on the ground to keep the antenna and ground lead within 3 meters.. however, it has been common practice for almost 40 years that all part15 installs have been 10 to 20 feet in the air in state parks, and none have ever been forced to comply with the 3 meter rule or discontinue operation. So take away from that what you will..

I have been tossing around the idea of attaching a 400 foot antenna wire to my drone, running it up to 400 feet and see what happens. Of course my drone has only 22 minutes of battery power so this would be a short range project!

Jim Henry's balloon idea for raising an antenna up in the air seems good in a fantasy imagination because it raises straight up and holds the antenna steady.

But you know how it is with the real world. Things don't always go the way you expect them to.

After thinking about it I now realize that the wind would make the balloon go east pulling the antenna which would yank the transmitter up into the air until the only thing holding it back would be outstreatched power and audio cables.

The wind would grow stronger and pull the cables free and the last time you would ever see your transmitter it would be rising into the night sky.

The next day there would be a story in the newspaper about an antenna dangling from a balloon wrapped around power lines causing a massive explosion and shutting down power to Atlanta.

I can truthfully testify that Druid Hills Radio was the first to suggest using a baloon.

What I saw happen next was Jim Henry agreed about using a baloon.

I sincerely don't think Jim was trying to take credit for originating the idea of the baloon, and when I suggested refinements and cautions about Jim's baloon concept, it would have been well to add a footnote crediting DHR with being the first with the baloon.

The best we can do is guard against such mis-credits in future threads.

Balloons aside, the question of how high your transmitter is, as already pointed out, is really a question of how long the ground. Even if you do not attach a ground lead, it will still be grounded (unless your running it on battery power..

I've mentioned this before, but as a 1981 TIS survey concluded (systems much like our own):

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"If the system makes use of commercial AC power, as nearly all do, the power ground will unavoidably become part of the antenna ground system. This may account for the fact that some antenna installations have been found to radiate tolerably well with what would otherwise appear to be a rather inefficient grounding."

No, the rules make no specific mention of groud being aquired by power or audio leads, but common sense does. If you have a transmitter 30-40 feet in the air with no "ground lead" attached, then your still going to have a 30-40 foot antenna system, it's just taking a different route.

The thing I find most frustratiing about 15.219 is that not even the certified transmitters, with particuar focus on the long established and most frequenty used transmitter used for the last 40 years -the Talking House, which was certified despite the fact that it never has ever actually conform to the 3 meter rule.. Rangemasters and Procasters do, but only if you install them at ground level and run via battery power.. And, as previously mentioned 40 years of common use of part 15 in state and federal parks, none of which even come cose to conforming to the 3 meters.

This has been eating the crap out of me lately.. If you wan't security that your install is 100% legal, well, that's almost impossible. The actual rules are apparently secondary, no one anywhere has ever complied to the letter.. It all based most entirely on if the inspecting agent decides he will allow it.

The most prudent you can be is to keep your range in check for a reasonabe unlicensed install.. if you are achieving over a mile radius then your getting into licenced low power ranges which obviously isn't kosher.

Of course this is all just my own deduced opinion based on research. I find the farce of 15.219 very disapointing, either rewrite it to conform with what has been clearly deemed acceptable to the FCC for the last 40 years, or enforce it as well as not certify transmitters which don't conform. Of course it's doubtful either will happen. My objective has been to insure legal operation, but the deeper I dig the more obvious it becomes that the FCC has decided that some are allowed to break the rules, but others have to obey it.

So how high can you have your transmitter mounted? To be honest that depends on where it's at and who you are and weather you're playing music or not.

About a year or two ago we had one come loose in Maryland and it came up here to South Central PA. It was an un-manned military observation blimp. I guess it didn't have one of those devices and it was dragging its steel tether which was a couple thousand feet long with it, doing considerable damage and ripping out highway guard rails along the way. It's a miracle that no one was killed.

For my part I very much appreciate the exploration you have done into all these compliance questions and your conclusions are very well reasoned and fit the picture of what has taken place in the part 15 experience over the years.

The only view I have of what's true and real regarding part 15 matches exactly what you have said.

Although I am sure it's in the background of your thoughts, I will also mention the factor of luck, which comes down to whether someone complains about you to the FCC.

If the FCC comes to inspect based on a complaint they might be more inclined to find a reason for shutting the station down to neutralize the complaint.

The issue of complaints is a whole dimension in itself. Some complaints are legitimate, such as an interfering station causing trouble to a licensed frequency.

Other complaints might be petty and jealous such as against a station that is causing no harm to licensed neighbors.

Exactly. Despite my frustrations expressed above, there's is also another consistentence of park and highway operation of part 15 which I should mention;

Back in the 1970's, height was from 10 to 30 feet and range was described as acheiving anywhere from 500 feet to a half-mile radius. The primary provider was INFO Systems provided by DTI

Around the 1990s I beleive LPB was the primary provider but I haven't really did much research about them but presume their outdoor free radiate sytems were also pole mounted elevated as most had always been. That's reasonable to assume.

Now in the present day similar systems height are described at height from 20 feet or roof mounted and acheiving anywhwere from 1/4 mile to 1/2 mile radius. The primary provider being ISS (however it can also be confirmed that both Procasters and Rangemasters are also used specifically in numerous Yellowstone campgrounds providing park info combined with NOAA weather reports.).

Point being that even though all of them appear to have always disregarded the 3 meter legnth restriction, their range has always been in check, and not excessive to compare with piracy.

I know first hand that a Rangemaster with about 15 foot ground lead that about a mile radius can be acheived without too much difficulty but that's about the best (in my ground conductivity of 8)... and thats only to decent a car radio and certainly not penetrating homes and buildings.

I'm just voicing frustrations and wonder where the legal line really is. My present conclusion is that line is blurred and always will be. But by observation it appears a half mile is fair game.

Again.. I'm only speaking observance, specuation and deductions.. The rules are hanging around here somewhere else.

Assuming the antenna is directly affixed to the transmitter the answer really becomes "how high can you get your transitter". Since your antenna and your antenna lead can equal only 3 meters, If your antenna was 1.5 meters, you could have it located 1.5 meters away from the transmitter itself. If you want your antenna at 30 feet, your transmitter will need to be at 30 feet as well, as you have no allowance left for antenna lead length.

This assuming you're running no ground lead at all.

As for those who always insist that if your transitter has power or audio leads that these are in fact ground leads, then virtually no part 15 transmitter ie legal unless your studio is underground and your wires connect to it at grouund level from under the Earth. Virtually all transmitters require power and sound be fed to them. Even a ground installed unit will have power and sound going to them, and even if they went from the transmitter on the ground into a ground floor window to the sound source, it would be over the ground length limit. For those believers, the only possible legal transmitter would be one with a build in USB port, with all the audio on the drive, and run on internal batteries or attached solar power. This is silly.

In the photos I've looked at from the submitted lab work for certification for virtually all the popular certified transmitters, they all have power and audio cables connected. So they were certified this way.

The answer is, as high is legal for something to go within your FAA and city, state and county codes tor tall things. Assuming you're not running a ground lead.

Assuming the antenna is directly affixed to the transmitter the answer really becomes "how high can you get your transitter". Since your antenna and your antenna lead can equal only 3 meters, if your antenna was 1.5 meters, you could have it located 1.5 meters away from the transmitter itself." ...

As far as physics is concerned, the wire conductor described above to be "your antenna" does not recognize that the "antenna lead," and all other conductors connected to the transmitter chassis or r-f ground terminal also can be part of that antenna.

Radiation from those added conductors can be several times greater than from the conductor some consider to be the complete antenna.

This was demonstrated by Tim's posted field strength measurements from several different FM transmitters when cables were/were not plugged into them.

TiminBovey said:"As for those who always insist that if your transitter has power or audio leads that these are in fact ground leads, then virtually no part 15 transmitter ie legal unless your studio is underground and your wires connect to it at grouund level from under the Earth. Virtually all transmitters require power and sound be fed to them. Even a ground installed unit will have power and sound going to them, and even if they went from the transmitter on the ground into a ground floor window to the sound source, it would be over the ground length limit. For those believers, the only possible legal transmitter would be one with a build in USB port, with all the audio on the drive, and run on internal batteries or attached solar power. This is silly.

In the photos I've looked at from the submitted lab work for certification for virtually all the popular certified transmitters, they all have power and audio cables connected. So they were certified this way.

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Excellent! Beautifully put, and illustrates my point exactly. If the objective is to be 100% legal as the rules dictate; you will find that it is impossible to do. It's been impossible to do all along. Yet in spite of that, the utilization 15.219 has consistently thrived with usefull and entertaining broadcast for over 40 years.

It is what it is. But if you recall a few months ago when someone had taken a Rangemaster or a Procaster and hiked it up some 50 feet or so in the air on a tower --with no ground lead attached-- (I forget the exact details but the whole discussion is in past threads here),. Anyway, with this setup he was acheiving something like 5 or 6 miles and he insisted it was completely in compliance with the rules...

At face value, he is correct. Per the rules he is acheiving greater range than even a licenced LPFM generally is capable of. But do you think a field agent would agree? Certainly not.

Thus the frustration. There is no certainy of compliance with any installation.